This is Rat Law: Cheese Belongs to You
Unless another rat comes along who is bigger, quicker, stronger, scarier, hairier, dirtier...or the boss wants it.

I can't say I love pictures of hair, scary, dirty rats, but I like that in essence it is a concept book in that it teaches adjectives through a fun medium. And unlike some recent picture books that I have read, there is a nice solution that encourages sharing rather than a all-mine attitude. I think this would be a perfect storytime book.